40 
K. L. PRENDERGAST. 
Strophalosia has a well-developed area on each valve, Aulosteges on the 
pedicle valve only, while ProducMis is without a true cardinal area. This 
distinction does not, of course, hold for all the Produetiis subgenera, in some 
of which, a cardinal area is developed. The non-dendritic adductor muscle 
impressions serve, however, to distinguish Stroi)}ialoMa from both Aulosteges 
and Productus as in tliese genera the adductors are alwaj^s dendritic. The 
posterior movement of the muscles and consequent change in pattern of the 
brachial impressions is also a typical Strophalosoid feature. 
Suhg(*ner a.— In recent years there has been much work done on tlie 
species of this genus, and it has now been subdivided into five subgejiera : — 
ETHERIDGINA Oehlert (— LEPTALOSIA Dunbar & Condra) 
STROPHALOSIINA Licbarew 
STROPHALOSIELLA Lii-harew 
WYNDHAMIA Booker 
HETERALOSIA King 
and with Aulosteges as a possible sixth or alternatively as a synonym. The 
relation of Aulosteges and Strophalosia has already been discussed (p. 34). 
Etheridglna includes those Strophalosias in which the shell is attached 
throughout the life of the animal, both by embracing spines and directly by 
the pedicle valve. A small cardinal area and teeth are sometimes, though 
not always present. Leptalosia, to include those forms possessing an area 
and teeth, cemented directly by the pedicle valve, was founded by Dunbar and 
Condra in 1932. Examination of the type specimens of Etheridgina com- 
plectens (Eth. til.), the genotype of Etheridgiue shows, however, that some 
of these specimens possess the hinge structures thought to be typical of 
Leptalosia. Leptalosia becomes, therefore, a synonym of Etheridgina. This 
question is more fully discussed under Etheridgina. 
The genotype of Strophalosiina Licharew is Aulosteges tihetius Diener. 
This species undoubtedly belongs to Aulosteges and is, under this system of 
classification, regarded as a subgenus of Aulosteges, 
Strophalosiella Licharew with genotype Strophulosiella coraeformis 
Licharew is a very doubtful genus. The specimen figured and described by 
Licharew is a plicate form (“a Strophalosia with Linoproductid ornamenta- 
tion^') with well-developed areas on both valves. In the absence of any 
knowledge of the internal structure it seems impossible to assign this speci- 
men to the genus Strophalosia. Until this knowledge is available it would 
seem better to maintain it as an independent genus of unknown affinities. 
Wyndhaonia was founded by Booker in 1929 for the reception of a group 
of Strophalosoid forms with adductor muscles undift'erentiated into anterior 
and posterior elements and without evidence of a period of attachment. The 
position of the muscle scars (]daced posteriorly in the valve) would indicate 
that the species of this subgenus (TE. vallda Booker and IE. dalwoodensis 
Booker) had attached ancestors, and had retained some of the ancestral 
characteristics, although they themselves had ceased to be attached. The 
assumption of these distinctive features, undifi'erentiated adductor muscle 
scars and absence of a cicatrix, is sufficient to characterise the subgenus. The 
type species of the subgenus is Wyndhamia dalwoodensis Booker from Per- 
mian beds of Branxton, New South Wales. 
In the same j)aper (1929, p. 30) Booker also proposed a new subgenus 
Bran.rtonia of Productus. The author has not been able to see the specimens 
of the genotype, Branxtonia typica Booker, but from Booker^s own figures 
and similar specimens from Western Australia, suspects that the specimens 
